William Blair Investment Management, LLC reported 389 positions worth $30.46B for the quarter ended Sep 30, 2026, down 7.8% on the prior quarter. It opened 41 new positions, added to 101, trimmed 244 and exited 42. Its largest holding is Taiwan Semiconductor Manufacturing Co Ltd at 6.9% of the portfolio.
Reported 13F market value at each quarter end. A change mixes trading with price moves in the positions held.
Dollar value of shares bought and sold each quarter, at that quarter’s price. It counts trading only, not price changes.
How many positions were opened, added to, trimmed or closed each quarter.
Share of reported value in each sector at every quarter end.
| Holding | Change | Change % | Trade Value | Weight |
|---|---|---|---|---|
| MU Micron Technology Inc | +210.3K | +1,496.1% | $224.04M | 0.785% |
| ESTC Elastic N.V. | +2.32M | – | $212.33M | 0.697% |
| GOOGL Alphabet Inc. | +417.0K | +13.1% | $143.50M | 4.08% |
| VSH Vishay Intertechnology Inc | +3.65M | +248.4% | $118.92M | 0.548% |
| MBGL Mobility Global Inc. | +5.29M | – | $90.74M | 0.298% |
| RGEN Repligen Corp | +454.8K | +57.7% | $87.43M | 0.785% |
| PCOR Procore Technologies, Inc. | +1.68M | – | $86.86M | 0.285% |
| LRCX Lam Research Corp | +261.7K | +255.9% | $85.98M | 0.393% |
| STX Seagate Technology Holdings plc | +86.1K | +45.1% | $79.45M | 0.839% |
| JLL Jones Lang Lasalle Inc | +243.3K | +338.6% | $74.33M | 0.316% |
| Holding | Change | Change % | Trade Value | Weight |
|---|---|---|---|---|
| TEVA Teva Pharmaceutical Industries Ltd | -6.59M | -100.0% | $223.37M | Exited |
| BWIN Baldwin Insurance Group, Inc. | -6.73M | -100.0% | $178.96M | Exited |
| MSFT Microsoft Corp | -337.2K | -16.5% | $172.96M | 2.88% |
| AMZN Amazon Com Inc | -654.3K | -32.9% | $163.01M | 1.09% |
| TSM Taiwan Semiconductor Manufacturing Co Ltd | -349.4K | -7.1% | $159.38M | 6.87% |
| AZN Astrazeneca Plc | -957.3K | -63.2% | $155.94M | 0.298% |
| SYNA SYNAPTICS Inc | -1.24M | -100.0% | $154.00M | Exited |
| SN SharkNinja, Inc. | -986.8K | -100.0% | $150.26M | Exited |
| TWST Twist Bioscience Corp | -720.5K | -33.1% | $139.22M | 0.922% |
| P Everpure, Inc. | -905.7K | -26.2% | $118.45M | 1.09% |
| Holding | Shares | Trade Value | Weight |
|---|---|---|---|
| ESTC Elastic N.V. | +2.32M | $212.33M | 0.697% |
| MBGL Mobility Global Inc. | +5.29M | $90.74M | 0.298% |
| PCOR Procore Technologies, Inc. | +1.68M | $86.86M | 0.285% |
| SGI Somnigroup International Inc. | +1.13M | $70.04M | 0.23% |
| TWLO Twilio Inc | +215.7K | $63.08M | 0.207% |
| ASO Academy Sports & Outdoors, Inc. | +1.17M | $56.41M | 0.185% |
| PBR Petrobras - Petroleo Brasileiro Sa | +2.66M | $55.46M | 0.182% |
| INSP Inspire Medical Systems, Inc. | +639.6K | $44.36M | 0.146% |
| SHOP Shopify Inc. | +287.0K | $42.57M | 0.14% |
| CP Canadian Pacific Kansas City Ltd | +499.6K | $42.52M | 0.14% |
| Holding | Shares Sold | Trade Value | Prior Weight |
|---|---|---|---|
| TEVA Teva Pharmaceutical Industries Ltd | -6.59M | $223.37M | 0.676% |
| BWIN Baldwin Insurance Group, Inc. | -6.73M | $178.96M | 0.542% |
| SYNA SYNAPTICS Inc | -1.24M | $154.00M | 0.466% |
| SN SharkNinja, Inc. | -986.8K | $150.26M | 0.455% |
| GTX Garrett Motion Inc. | -3.23M | $117.13M | 0.354% |
| MLM Martin Marietta Materials Inc | -181.9K | $104.90M | 0.317% |
| HLIO Helios Technologies, Inc. | -834.2K | $74.45M | 0.225% |
| KMT Kennametal Inc | -1.99M | $69.61M | 0.211% |
| CIEN Ciena Corp | -133.8K | $65.64M | 0.199% |
| AMX America Movil Sab De Cv/ | -2.01M | $52.25M | 0.158% |
| # | Activity | ||||||||
|---|---|---|---|---|---|---|---|---|---|
| 1 | TSM Taiwan Semiconductor Manufacturing Co Ltd | Technology | 4.59M | $2.09B | 6.87% | -349.4K | -7.1% | Reduced | 0.02% |
| 2 | NVDA Nvidia Corp | Technology | 8.12M | $1.86B | 6.09% | -475.4K | -5.5% | Reduced | 0.03% |
| 3 | GOOGL Alphabet Inc. | Technology | 3.61M | $1.24B | 4.08% | +417.0K | +13.1% | Added | 0.05% |
| 4 | AAPL Apple Inc. | Technology | 3.02M | $1.01B | 3.3% | -237.1K | -7.3% | Reduced | 0.02% |
| 5 | MSFT Microsoft Corp | Technology | 1.71M | $877.79M | 2.88% | -337.2K | -16.5% | Reduced | 0.02% |
| 6 | AVGO Broadcom Inc. | Technology | 1.98M | $696.53M | 2.29% | -72.8K | -3.5% | Reduced | 0.04% |
| 7 | META Meta Platforms, Inc. | Technology | 806.8K | $585.06M | 1.92% | -143.3K | -15.1% | Reduced | 0.03% |
| 8 | AMD Advanced Micro Devices Inc | Technology | 783.2K | $479.13M | 1.57% | +19.7K | +2.6% | Added | 0.05% |
| 9 | MA Mastercard Inc | Financial Services | 707.6K | $390.25M | 1.28% | -210.4K | -22.9% | Reduced | 0.08% |
| 10 | P Everpure, Inc. | Technology | 2.55M | $333.45M | 1.09% | -905.7K | -26.2% | Reduced | 0.76% |
| 11 | AMZN Amazon Com Inc | Consumer Discretionary | 1.33M | $332.07M | 1.09% | -654.3K | -32.9% | Reduced | 0.01% |
| 12 | AMAT Applied Materials Inc | Technology | 606.3K | $310.07M | 1.02% | +108.4K | +21.8% | Added | 0.08% |
| 13 | TWST Twist Bioscience Corp | Healthcare | 1.45M | $280.99M | 0.922% | -720.5K | -33.1% | Reduced | 2.32% |
| 14 | CG Carlyle Group Inc. | Financial Services | 6.82M | $270.54M | 0.888% | +906.7K | +15.3% | Added | 1.91% |
| 15 | GE General Electric Co | Industrials | 854.9K | $266.98M | 0.876% | +64.1K | +8.1% | Added | 0.08% |
Tip. Select a row to see that position’s full history at William Blair Investment Management.
As of its Q3 2026 13F filing, William Blair Investment Management, LLC’s five largest positions were Taiwan Semiconductor Manufacturing Co Ltd (TSM) at 6.9%, Nvidia Corp (NVDA) at 6.1%, Alphabet Inc. (GOOGL) at 4.1%, Apple Inc. (AAPL) at 3.3%, Microsoft Corp (MSFT) at 2.9% of the reported portfolio.
William Blair Investment Management, LLC reported a 13F portfolio worth $30.46B across 389 positions for Q3 2026. That is down 7.8% from the previous quarter.
Its largest purchases by value were Micron Technology Inc ($224.04M), Elastic N.V. ($212.33M), Alphabet Inc. ($143.50M). It opened 41 new positions.
Its largest sales by value were Teva Pharmaceutical Industries Ltd ($223.37M), Baldwin Insurance Group, Inc. ($178.96M), Microsoft Corp ($172.96M). It exited 42 positions entirely.
From the Form 13F-HR reports William Blair Investment Management, LLC files with the SEC each quarter, within 45 days of quarter end. A 13F lists long positions in US-listed equities and options; it excludes short positions, cash, bonds and most non-US holdings.
13F data reflects long positions in US-listed equities and options as reported to the SEC up to 45 days after quarter end. It excludes short positions, cash, bonds and most non-US securities, so it is not a complete picture of a manager’s assets.